From the U.S. Pat. No. 4,139,751 is known a compressed-gas circuit breaker which contains a contact system and a blast device which is assigned to the contact system. The blast device has a fixed, ring shaped piston and a movable cylinder. The piston is sealed via a first sealing ring against the cylinder and via a second sealing ring against a movable cylindrical switching element of the contact system. The circuit breaker further contains a non-return or one-way valve, which is closed in the compression phase and opened in the intake phase of the circuit breaker. In this circuit breaker the one-way valve is formed by apertures in the outer annular portion of the fixed piston which may be closed by spring-loaded combinations of annular rings and rods (see U.S. Pat. No. 4,139,751, FIG. 7). In the compression phase, the force of the valve springs is supported by the gas, and the apertures are kept closed. In the intake phase, the force of the valve springs is overcome, and the apertures are opened.
The British Pat. No. 1,510,399 discloses a compressed-gas circuit breaker which also contains a blast device having a fixed piston and a movable cylinder. The circuit breaker further contains two stationary contacts which are electrically connected with each other by a bridging switching element in the closing position. In this circuit breaker there are provided two sealing rings in the plane transverse to the axis of the piston. One of the sealing rings engages the blast cylinder, and the other sealing ring engages the movable cylindrical switching element of the contact system. In this circuit breaker, a one-way valve is not provided.
The German Offenlegengschrift No. 25 41 851 describes a feed or booster pump for application as a blast device for quenching gas in compressed-gas circuit breakers for high voltage. The pump contains a one-way valve that is formed by a piston ring. The piston ring is located in an annular groove which is arranged in the piston. The piston ring has some space and is spring biased in the axial direction of the piston. Under the effect of the springs, the piston ring closes openings in the piston which connect the pressure side with the vacuum side of the piston. Thereby, the cylinder surrounds the piston in a sealed, pressure-tight manner when the piston is moved in the direction of transportation of the pumped medium, whereas this pressure-tight seal is eliminated in the reverse direction.